//===--- SideEffectAnalysis.h - PIL Side Effect Analysis --------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#ifndef POLARPHP_PIL_OPTIMIZER_ANALYSIS_SIDEEFFECTANALYSIS_H
#define POLARPHP_PIL_OPTIMIZER_ANALYSIS_SIDEEFFECTANALYSIS_H

#include "polarphp/pil/lang/ApplySite.h"
#include "polarphp/pil/lang/PILInstruction.h"
#include "polarphp/pil/lang/PILFunction.h"
#include "polarphp/pil/optimizer/analysis/BottomUpIPAnalysis.h"
#include "polarphp/pil/optimizer/analysis/ArraySemantic.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"

namespace polar {

class BasicCalleeAnalysis;


/// An enum to represent the kind of scan we perform when we calculate
/// side effects.
enum class RetainObserveKind {
   ObserveRetains,
   IgnoreRetains,
   RetainObserveKindEnd
};

/// Generic base class for any bottom up analysis that summarizes per-function
/// "effects" by first computing local effects, then propagating those effects
/// bottom-up through the call graph.
///
/// FunctionEffects constraints:
/// - void clear()
/// - void setWorstEffects()
/// - bool summarizeFunction(PILFunction *)
/// - bool summarizeCall(FullApplySite)
/// - bool mergeFrom(const FunctionSideEffects &)
/// - bool mergeFromApply(const FunctionEffects &, FullApplySite)
/// - void analyzeInstruction(PILInstruction *)
template <typename FunctionEffects>
class GenericFunctionEffectAnalysis : public BottomUpIPAnalysis {

   /// Stores the analysis data, e.g. side-effects, for a function.
   struct FunctionInfo : public FunctionInfoBase<FunctionInfo> {

      /// The function effects.
      FunctionEffects functionEffects;

      /// Back-link to the function.
      PILFunction *F;

      /// Used during recomputation to indicate if the side-effects of a caller
      /// must be updated.
      bool needUpdateCallers = false;

      FunctionInfo(PILFunction *F) : F(F) {}

      /// Clears the analysis data on invalidation.
      void clear() { functionEffects.clear(); }
   };

   typedef BottomUpFunctionOrder<FunctionInfo> FunctionOrder;

   enum {
      /// The maximum call-graph recursion depth for recomputing the analysis.
      /// This is a relatively small number to reduce compile time in case of
      /// large cycles in the call-graph.
      /// In case of no cycles, we should not hit this limit at all because the
      /// pass manager processes functions in bottom-up order.
         MaxRecursionDepth = 5
   };

   /// All the function effect information for the whole module.
   llvm::DenseMap<PILFunction *, FunctionInfo *> functionInfoMap;

   /// The allocator for the map of values in FunctionInfoMap.
   llvm::SpecificBumpPtrAllocator<FunctionInfo> allocator;

   /// Callee analysis, used for determining the callees at call sites.
   BasicCalleeAnalysis *BCA;

public:
   GenericFunctionEffectAnalysis(PILAnalysisKind kind)
      : BottomUpIPAnalysis(kind) {}

   const FunctionEffects &getEffects(PILFunction *F) {
      FunctionInfo *functionInfo = getFunctionInfo(F);
      if (!functionInfo->isValid())
         recompute(functionInfo);
      return functionInfo->functionEffects;
   }

   /// Get the merged effects of all callees at the given call site from the
   /// callee's perspective (don't transform parameter effects).
   void getCalleeEffects(FunctionEffects &calleeEffects,
                         FullApplySite fullApply);

   /// Get the merge effects of all callees at the given call site from the
   /// caller's perspective. Parameter effects are translated into information
   /// for the caller's arguments, and local effects are dropped.
   void getCallSiteEffects(FunctionEffects &callEffects,
                           FullApplySite fullApply) {
      FunctionEffects calleeEffects;
      getCalleeEffects(calleeEffects, fullApply);
      callEffects.mergeFromApply(calleeEffects, fullApply);
   }

   virtual void initialize(PILPassManager *PM) override;

   /// Invalidate all information in this analysis.
   virtual void invalidate() override;

   /// Invalidate all of the information for a specific function.
   virtual void invalidate(PILFunction *F, InvalidationKind K) override;

   /// Notify the analysis about a newly created function.
   virtual void notifyAddedOrModifiedFunction(PILFunction *F) override {}

   /// Notify the analysis about a function which will be deleted from the
   /// module.
   virtual void notifyWillDeleteFunction(PILFunction *F) override {
      invalidate(F, InvalidationKind::Nothing);
   }

   /// Notify the analysis about changed witness or vtables.
   virtual void invalidateFunctionTables() override {}

private:
   /// Gets or creates FunctionEffects for \p F.
   FunctionInfo *getFunctionInfo(PILFunction *F) {
      FunctionInfo *&functionInfo = functionInfoMap[F];
      if (!functionInfo) {
         functionInfo = new (allocator.Allocate()) FunctionInfo(F);
      }
      return functionInfo;
   }

   /// Analyze the side-effects of a function, including called functions.
   /// Visited callees are added to \p BottomUpOrder until \p RecursionDepth
   /// reaches MaxRecursionDepth.
   void analyzeFunction(FunctionInfo *functionInfo, FunctionOrder &bottomUpOrder,
                        int recursionDepth);

   void analyzeCall(FunctionInfo *functionInfo, FullApplySite fullApply,
                    FunctionOrder &bottomUpOrder, int recursionDepth);

   /// Recomputes the side-effect information for the function \p Initial and
   /// all called functions, up to a recursion depth of MaxRecursionDepth.
   void recompute(FunctionInfo *initialInfo);
};

/// Set \p dest if \p src is set and return true if \p dest was not set
/// before.
static bool changedFlagByInPlaceOr(bool &dest, bool src) {
   if (src && !dest) {
      dest = src;
      return true;
   }
   return false;
}

/// Side-effect information for the function (global effects) or a specific
/// parameter of the function. See FunctionSideEffects.
class FunctionSideEffectFlags {
   friend class FunctionSideEffects;
   using MemoryBehavior = PILInstruction::MemoryBehavior;

   bool Reads = false;
   bool Writes = false;
   bool Retains = false;
   bool Releases = false;

   /// Sets the most conservative effects.
   void setWorstEffects() {
      Reads = true;
      Writes = true;
      Retains = true;
      Releases = true;
   }

   /// Clears all effects.
   void clear() {
      Reads = false;
      Writes = false;
      Retains = false;
      Releases = false;
   }

public:
   /// Does the function read from memory (excluding reads from locally
   /// allocated memory)?
   bool mayRead() const { return Reads; }

   /// Does the function write to memory (excluding writes to locally
   /// allocated memory)?
   bool mayWrite() const { return Writes; }

   /// Does the function retain objects (excluding retains of locally
   /// allocated objects)?
   bool mayRetain() const { return Retains; }

   /// Does the function release objects (excluding releases of locally
   /// allocated objects)?
   bool mayRelease() const { return Releases; }

   /// Gets the memory behavior considering the global effects and
   /// all parameter effects. If \p ScanKind equals ignoreRetains then retain
   /// instructions are considered as side effects.
   MemoryBehavior getMemBehavior(RetainObserveKind ScanKind) const {
      if (mayRelease())
         return MemoryBehavior::MayHaveSideEffects;

      if (ScanKind == RetainObserveKind::ObserveRetains && mayRetain())
         return MemoryBehavior::MayHaveSideEffects;

      if (mayWrite())
         return mayRead() ? MemoryBehavior::MayReadWrite
                          : MemoryBehavior::MayWrite;

      if (mayRead())
         return MemoryBehavior::MayRead;

      return MemoryBehavior::None;
   }

   /// Merge effects from \p RHS.
   bool mergeFrom(const FunctionSideEffectFlags &RHS) {
      bool Changed = false;
      Changed |= changedFlagByInPlaceOr(Reads, RHS.Reads);
      Changed |= changedFlagByInPlaceOr(Writes, RHS.Writes);
      Changed |= changedFlagByInPlaceOr(Retains, RHS.Retains);
      Changed |= changedFlagByInPlaceOr(Releases, RHS.Releases);
      return Changed;
   }

   friend raw_ostream &operator<<(raw_ostream &os,
                                  const FunctionSideEffectFlags &Effects) {
      if (Effects.mayRead())
         os << 'r';
      if (Effects.mayWrite())
         os << 'w';
      if (Effects.mayRetain())
         os << '+';
      if (Effects.mayRelease())
         os << '-';
      return os;
   }
};

/// Summarizes the side-effects of a function. The side-effect information
/// is divided into global effects and effects for specific function
/// parameters.
/// If a side-effect can be associated to a specific function parameter, it is
/// not added to the global effects of the function. E.g. if a memory write is
/// only done through an @inout parameter, the mayWrite side-effect is only
/// accounted for this parameter.
/// Effects for a parameter make only sense if the parameter is implemented as
/// a pointer or contains a pointer:
/// *) The parameter is an address parameter, e.g. @out, @inout, etc.
/// *) The parameter is a reference
/// *) The parameter is a value type (e.g. struct) and contains a reference.
///    In this case the effects refer to all references in the value type.
///    E.g. if a struct contains 2 references, a mayWrite effect means that
///    memory is written to one of the referenced objects (or to both).
class FunctionSideEffects {
   using MemoryBehavior = PILInstruction::MemoryBehavior;

   /// Side-effects which can be associated to a parameter.
   llvm::SmallVector<FunctionSideEffectFlags, 6> ParamEffects;

   /// All other side-effects which cannot be associated to a parameter.
   FunctionSideEffectFlags GlobalEffects;

   /// Side-effects on locally allocated storage. Such side-effects are not
   /// relevant to optimizations. The LocalEffects are only used to return
   /// "something" for local storage in getEffectsOn().
   FunctionSideEffectFlags LocalEffects;

   /// Does the function allocate objects, boxes, etc., i.e. everything which
   /// has a reference count.
   bool AllocsObjects = false;

   /// Can this function trap or exit the program in any way?
   bool Traps = false;

   /// Does this function read a reference count other than with retain or
   /// release instructions, e.g. isUnique?
   bool ReadsRC = false;

   /// Returns the effects for an address or reference. This might be a
   /// parameter, the LocalEffects or, if the value cannot be associated to one
   /// of them, the GlobalEffects.
   FunctionSideEffectFlags *getEffectsOn(PILValue Addr);

public:
   /// Constructs "empty" function effects. This effects object can later be
   /// populated by summarizeFunction or summarizeCall.
   FunctionSideEffects() {}

   /// Sets the most conservative effects, if we don't know anything about the
   /// function.
   void setWorstEffects() {
      GlobalEffects.setWorstEffects();
      AllocsObjects = true;
      Traps = true;
      ReadsRC = true;
   }

   /// Clears all effects.
   void clear() {
      ParamEffects.clear();
      GlobalEffects.clear();
      AllocsObjects = false;
      Traps = false;
      ReadsRC = false;
   }

   /// Merge the flags from \p RHS.
   bool mergeFlags(const FunctionSideEffects &RHS) {
      bool Changed = false;
      Changed |= changedFlagByInPlaceOr(Traps, RHS.Traps);
      Changed |= changedFlagByInPlaceOr(AllocsObjects, RHS.AllocsObjects);
      Changed |= changedFlagByInPlaceOr(ReadsRC, RHS.ReadsRC);
      return Changed;
   }

   // Summarize the given function's effects using this FunctionSideEffects
   // object.
   //
   // Return true if the function's' effects have been fully summarized without
   // visiting it's body.
   bool summarizeFunction(PILFunction *F);

   /// Summarize the callee side effects of a call instruction using this
   /// FunctionSideEffects object without analyzing the callee function bodies or
   /// scheduling the callees for bottom-up propagation.
   ///
   /// The side effects are represented from the callee's perspective. Parameter
   /// effects are not translated into information on the caller's argument, and
   /// local effects are not dropped.
   ///
   /// Return true if this call-site's effects are summarized without visiting
   /// the callee.
   bool summarizeCall(FullApplySite fullApply);

   /// Merge effects directly from \p RHS.
   bool mergeFrom(const FunctionSideEffects &RHS);

   /// Merge the effects represented in CalleeEffects into this
   /// FunctionSideEffects object. CalleeEffects must correspond to at least one
   /// callee at the apply site `FAS`. Merging drops any local effects, and
   /// translates parameter effects into effects on the caller-side arguments.
   ///
   /// The full caller-side effects at a call site can be obtained with
   /// SideEffectsAnalysis::getCallSiteEffects().
   bool mergeFromApply(const FunctionSideEffects &CalleeEffects,
                       FullApplySite FAS);

   /// Analyze the side-effects of a single PIL instruction \p I.
   /// Visited callees are added to \p BottomUpOrder until \p RecursionDepth
   /// reaches MaxRecursionDepth.
   void analyzeInstruction(PILInstruction *I);

   /// Print the function effects.
   void dump() const;

   /// Does the function allocate objects, boxes, etc., i.e. everything which
   /// has a reference count.
   bool mayAllocObjects() const { return AllocsObjects; }

   /// Can this function trap or exit the program in any way?
   bool mayTrap() const { return Traps; }

   /// Does this function read a reference count other than with retain or
   /// release instructions, e.g. isUnique?
   bool mayReadRC() const { return ReadsRC; }

   /// Gets the memory behavior considering the global effects and
   /// all parameter effects. If \p ScanKind equals ignoreRetains then retain
   /// instructions are considered as side effects.
   MemoryBehavior getMemBehavior(RetainObserveKind ScanKind) const;

   /// Get the global effects for the function. These are effects which cannot
   /// be associated to a specific parameter, e.g. writes to global variables
   /// or writes to unknown pointers.
   const FunctionSideEffectFlags &getGlobalEffects() const {
      return GlobalEffects;
   }

   /// Get the array of parameter effects. If a side-effect can be associated
   /// to a specific parameter, it is contained here instead of the global
   /// effects.
   /// Note that if a parameter effect is mayRelease(), it means that the
   /// global function effects can be anything, because the destructor of an
   /// object can have arbitrary side effects.
   ArrayRef<FunctionSideEffectFlags> getParameterEffects() const {
      return ParamEffects;
   }

protected:
   /// Set the side-effects of a function, which has an @_effects attribute.
   /// Returns true if \a F has an @_effects attribute which could be handled.
   bool setDefinedEffects(PILFunction *F);

   /// Set the side-effects of a semantic call.
   /// Return true if \p ASC could be handled.
   bool setSemanticEffects(ArraySemanticsCall ASC);

   friend raw_ostream &operator<<(raw_ostream &os,
                                  const FunctionSideEffects &Effects) {
      os << "func=" << Effects.getGlobalEffects();
      int ParamIdx = 0;
      for (auto &E : Effects.getParameterEffects()) {
         os << ",param" << ParamIdx++ << "=" << E;
      }
      if (Effects.mayAllocObjects())
         os << ";alloc";
      if (Effects.mayTrap())
         os << ";trap";
      if (Effects.mayReadRC())
         os << ";readrc";
      return os;
   }
};

/// The SideEffectAnalysis provides information about side-effects of PIL
/// functions. Side-effect information is provided per function and includes:
/// Does the function read or write memory? Does the function retain or release
/// objects? etc.
/// For details see FunctionSideEffects.
class SideEffectAnalysis
   : public GenericFunctionEffectAnalysis<FunctionSideEffects> {
public:
   SideEffectAnalysis()
      : GenericFunctionEffectAnalysis<FunctionSideEffects>(
      PILAnalysisKind::SideEffect) {}

   static bool classof(const PILAnalysis *S) {
      return S->getKind() == PILAnalysisKind::SideEffect;
   }
};

} // end namespace polar::pilSimplifyInstruction.h

#endif // POLARPHP_PIL_OPTIMIZER_ANALYSIS_SIDEEFFECTANALYSIS_H
